Turbocharged and supercharged engines may be configured to compress ambient air entering the engine in order to increase power. Compression of the air may cause an increase in air temperature, thus, a charge air cooler may be utilized to cool the heated air thereby increasing its density and further increasing the potential power of the engine. Ambient air from outside the vehicle travels across the CAC to cool intake air passing through the inside of the CAC. Condensate may form in the CAC when the ambient air temperature decreases, or during humid or rainy weather conditions, where the intake air is cooled below the water dew point. Condensate may collect at the bottom of the CAC, or in the internal passages, and cooling turbulators. When torque is increased, such as during acceleration, increased mass air flow may strip the condensate from the CAC, drawing it into the engine and increasing the likelihood of engine misfire.
Other attempts to address engine misfire due to condensate ingestion involve avoiding condensate build-up. However, the inventors herein have recognized potential issues with such methods. Specifically, while some methods may reduce or slow condensate formation in the CAC, condensate may still build up over time. If this build-up cannot be stopped, ingestion of the condensate during acceleration may cause engine misfire. Another method to prevent engine misfire due to condensate ingestion includes trapping and/or draining the condensate from the CAC. While this may reduce condensate levels in the CAC, condensate is moved to an alternate location or reservoir, which may be subject to other condensate problems such as freezing and corrosion.
In one example, the issues described above may be addressed by a method for purging condensate from a CAC during an acceleration event. For example, during the acceleration event, when the condensate level in the CAC is above a threshold level, a controller may limit an increase in engine airflow. In this way, the rate of condensate ingestion into the engine may be controlled, reducing the chance of engine misfire, or unstable combustion.
As one example, when the condensate level in the CAC is above a first threshold level, an increase in engine airflow may be limited during an acceleration event. The acceleration event may include a tip-in and be indicated by an increase in pedal position beyond a threshold. The limiting of engine airflow may include controlling the opening of a throttle to a determined rate of increase in engine airflow. This rate of increase in engine airflow may be adjusted based on the level of condensate in the CAC and a target condensate ingestion rate. Limiting of engine airflow may stop when the condensate level in the charge air cooler decreases below a second threshold level.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.